<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>my css3</title>
    <link rel="stylesheet" href="mycss3.css">
</head>
<body>
<p>这是一些<span class="blue">文字</span>。</p>
<p class="blue">蓝色</p>
<h2 class="blue">2号标题</h2>

<p class="orange">橙色</p>
<p class="green">绿色</p>
<p class="orange green">颜色由样式表文件中class的先后顺序决定</p>
</body>
</html>